Rotary potentiometer

ABSTRACT

In a ganged potentiometer assembly, two elements containing a resistance track and a collector track are rigidly and nonrotatably mounted in support structure in spaced opposition to each other. An intermediate, rotatable wheel, loosely journaled on a shaft that extends between the two potentiometer elements, is provided with opposite facing wiper means which are in contact with the resistance and the collector tracks.

United States Patent Wormser [451 June 20,1972

[54] ROTARY POTENTIOMETER [72] Inventor: Hans 11. Wormser, New Milford, NJ.

[73] Assignee: Marldte Corporation, New York, NY.

[22] Filed: Nov. 10, 1969 [21] Appl. No.: 875,314

[52] US. Cl ..338/131, 338/132 1 1 [58] FleldofSearch ..338/l28,130,l31,132,133

[56] References Clted UNITED STATES PATENTS 2,434,248 1/1948 Mucher ..338/132X 2,959,729 11/1960 Karg ..338/l30 X Primary E.\'aminer--Lewis H. Myers Assistant Eraminer-D. A. Tone Attorney-Leonard H. King [57] ABSTRACT 15 Claims, 7 Drawing Figures PflTENTEnJuuzo m2 SHEET 1 OF 2 FIG. 4

INVENTOR. HANS H. WORMSER Arron/vs) PATEmEnJum m2 3, 571 ,914

sum 2 OF 2 INVENTOR. HANS H WORMSE'R ATTORNEY ROTARY POTENTIOMETER The aforementioned abstract is neither intended to define the invention of the application which, of course, is measured by the claims, nor is it intended to be limiting as to the scope of the invention in any way.

This invention relates generally to variable resistance devices and more particularly to improved construction of rotary ganged potentiometers.

In its broadest aspect the present invention provides that the resistance elements and collectors in a gangedpotentiometer are rigidly held so as to prevent rotation thereof. A shaft extends through the two axially spaced apart potentiometer elements and supports therebetween a wheel on which is mounted wiper means for contacting the resistance and collector tracks. Keying means on the resistance element assemblies mate with similarly shaped recesses in support means for preventing rotation of the tracks. The shaft is round and float ing in order to provide for the best fit at the lowest cost and to maintaina common center between the wipers and the tracks. Spring means are compressed so as to provide for its exertion of a known force at assembly in order to control torque requirements without the need for close axial tolerances. The rotatable wheel that carries the wiper means may be single for common actuation of both wipers or may be in two parts to permit independent actuation of each wiper.

As mentioned above the present invention provides means for holding the element directly in the support member. By way of contrast, the prior art used a D shaft which was keyed to the resistance element so as to indirectly hold theelement. However, the D shaft is more expensive to manufacture and, in addition, does not provide the improved concentricity available with the present invention.

Accordingly, it is a primary object of the present invention to provide an improved rotary potentiometer.

It is another object of this invention to provide an improved gangedrotary potentiometer.

Still another object of this invention is to provide an improved potentiometer, as described above, wherein the resistance element assembly is directly held and prevented from rotating. 7

A further object of this invention is to provide an improved potentiometer, as described above, wherein there is provided a wheel positioned intermediate two rigidly held potentiometer resistance assemblies, the wheel being loosely mounted on the shaft common to the resistance element assemblies and carrying wiper means.

Still another object of this invention is to provide, as described above, a single wheel for concurrently rotating both wipers in a ganged potentiometer assembly.

A further object of this invention is to provide, as described above, independently rotatable wheels.

An additional object of this invention is to provide means for axially loading the common shaft of a common ganged potentiometer assembly to minimize the need for close axial tolerances.

A specific object of this invention is to provide a ganged potentiometer assembly, as described above, that utilizes a round shaft as opposed to a D shaft.

These and other objects, features and advantages of the invention will, in part be pointed out with particularity, and will, in part, become obvious from the following more detailed description of the invention, taken in conjunction with the accompanying drawing, which forms an integral part thereof.

In the various figures of the drawing like reference characters designate like parts.

In the drawing:

FIG. I is an end elevational view of a ganged potentiometer formed in accordance with the teachings of this invention;

FIG. 2 is a sectional side elevational view taken along line 2-2 of FIG. 1;

FIG. 3 is an end elevational view, partly in section, taken along line 3-3 of FIG. 2;

FIG. 4 is a fragmentary, sectional detailed view, in elevation taken along line 4-4 of FIG. 3;

FIG. 5 is a sectional elevational view of the resistance element assembly comprising the present invention;

FIG. 6 is an end elevation view of the structure shown in FIG. 5; and

FIG. 7 is a sectional elevational view similar to FIG. 2, but with portions omitted for clarity, illustrating an alternative embodiment of this invention.

Turning now to the drawings, there is shown in FIGS. [-6 the first embodiment of a dual, ganged potentiometer 10. The basic sub-assembly of the potentiometer 10 comprises a centrally located disc-like member or wheel 12 that is positioned intermediate the two resistance element assemblies 14 and 14'. For purposes of this discussion the .wheel 12 will be described first.

Wheel 12 is a molded plastic member which, on its periphery, may be provided with ridges 16 in order to facilitate manual rotation thereof. The wheel 12 has a central bore 18 for loosely receiving a round shaft 20. An annular recess 22 is provided in opposite transverse end surfaces of the wheel 12 in order to permit assembly therein of a resilient metallic wiper member 24 having a first pair of fingers 26 and a second pair of fingers 28. As shown particularly in FIG. 3 and in FIG. 4 the wiper is secured in the annular recess 22. To simplify this assembly the wiper 24 is provided with a notch 30 in which is received a boss 32 that is integral with the surface of the wheel 12. By means of any tool, such as a heated red, the boss 32 may be deformed so as to overlay and grip the wiper 24. FIG. 4 illustrates the boss 32 both before and after its deformation. Finally, and for purposes to be discussed hereinafter, axially extending tabs 34 are provided on opposite facing planar surfaces of the wheel 12 at a location radially outward of the annular recesses 22.

The resistance element assemblies 14 and 14' are each com prised of a disc-like molded plastic insulator base member 40. In the assembled condition the outer surface of the base member is provided with a keying member 42 which in the embodiment illustrated is rectangular in transverse cross-section. A central bore 44 is also provided in the base member, the bore 44 opening into an enlarged recess 46 in the keying member 42. The opposite surface of the base member 40 is provided with a seat 48 that is arranged to receive a resistance element generally designated by the reference character 50, The base member and resistance element may be combined within the scope of the invention.

A brass drive pin 52 (FIG. 5) is used to secure the resistance element 50 to the base member 40. The resistance element 50 is comprised of a conductive plastic resistance track 54 and a conductive collector track 56. The conductive plastic track may be sprayed onto the substrate and/or comolded thereto by anyone of the known means as for example as taught in US. Pat. No. 3,371,138. Terminal means 58 and 60 are positioned in grooves 62 formed in the base member 40 and holes 64 formed in the resistance element 50 proximate the ends of the resistance track 54. If desired the terminals 58 and 60 may be comolded with the element holders 14. After assembly of the resistance element assembly 50, as described above, the grooves 62 are deformed by the application of heat in order to retain the terminals 58 and 60. Alternatively, instead of deforming the grooves, an adhesive may be used to secure the resistance element in position. Finally, the resistance element assemblies 50 are each provided with a radially extending tab 66 that is adapted to cooperate with the tabs 34 formed on the wheel 12 so as to limit angular movement thereof.

The present invention is assembled by inserting the shaft 20 into the bores 18 and 44 of the wheel 12 and the resistance element assembly 14, respectively. As shown particularly in FIG. 2, flat washers 70 and 70 are placed about the shaft 20 at the base of the recesses 46 and 46'. At the left-hand side a bowed resilient washer 72 is positioned opposite the washer 70; it is retained in this position by means of a retaining washer 74. The spring-like washer 72 is compressed to a pre-determined pressure and then a second retaining washer 74 is affixed to the opposite end of the shaft 20 within the recess 46' so as to minimize relative axial movement between the wheel 12 and the resistance element assemblies 14 and 14'. This method of assembly permits control of torque without the necessity of maintaining tight axial tolerances in the manufacturing process.

From the foregoing it will be appreciated that an extremely simple assembly has been evolved for a ganged potentiometer. The present invention permits the usage of a more accurately machined and lower cost shaft as opposed to the prior art usage of a D shaped shaft. The non-circular keying members provide that the resistance element assemblies are directly held as opposed to the prior art structure of holding the resistance element indirectly by means of a shaft. It should be understood that the wheel 12 is loose on the shaft 20 and may easily be rotated by hand so that the wiper means may traverse the resistance and collector tracks which are stationary.

Turning now to FIG. 7 there is shown an alternative embodiment of the present invention. Whereas the first embodiment utilized a solid wheel having wiper means on opposed faces thereof, the second embodiment uses independent wheels 80 and 82 each of which has its own wiper means 84 and 86 secured in the same manner as described in connection with the previous embodiment. A spacer member 88 may be positioned intermediate the two wheels 80 and 82. The remaining construction of the wheels 80 and 82 together with the resistance element assemblies that are coupled thereto are the same as has been described hereinabove. This second embodiment of the present invention permits independent rotation of the wiper means 84 and 86.

There has been disclosed heretofore the best embodiment of the invention presently contemplated. However, it is to be understood that various changes and modifications may be made thereto without departing from the spirit of the invention.

What I claim as new and desire to secure by Letters patent is:

1. A ganged potentiometer comprising:

a. a non-conductive wheel means having electrically conductive wiper means secured thereto and facing in axially opposite directions;

b. a shaft extending through and supporting said wheel means for rotation about the axis thereof;

c. a resistance element assembly mounted on said shaft proximate each end thereof, each said resistance element assembly including a non-conductive plastic base member, conductive plastic resistance track means and collector track means integral with said base member so as to be in contact with said wiper means during rotation of said wheel and terminal means adapted to electrically connect said resistance element assembly to a utilization device;

d. key means integral with each said resistance element assembly and adapted to mate with a receptacle in a support member whereby rotation of said resistance element assemblies are prevented relative to said wheel; and

e. fastener means for minimizing relative axial movement of said resistance element assemblies and said wheel.

2. The potentiometer in accordance with claim 1 wherein said wheel means is one piece and is loosely mounted on said shaft.

3. The potentiometer in accordance with claim 1 wherein said wheel means is comprised of two separate and independent members, a wiper means being secured to each of said members.

4. The potentiometer in accordance with claim 3 wherein said members are loosely mounted on said shaft.

5. The potentiometer in accordance with claim 4 wherein there is further included spacer means intermediate said members.

6. The potentiometer in accordance with claim 1 wherein said wheel means includes heat deformable boss means for securing said wiper means thereto.

7. The potentiometer in accordance with claim 1 wherein said resistance element assemblies are loosely mounted on said shaft.

8. The potentiometer in accordance with claim 1 wherein said resistance and collector track means are comolded with said base means.

9. The potentiometer in accordance with claim 1 wherein said base members include heat deformable recesses for securing said terminal means thereto.

10. The potentiometer in accordance with claim 1 wherein said key means comprises a non-circular boss extending from said base member in an axial direction away from said wheel.

11. The potentiometer in accordance with claim 10, wherein said boss is rectangular.

12. The potentiometer in accordance with claim 11 where the axis of said boss coincides with the axis of said shaft.

13. The potentiometer in accordance with claim 1 wherein there is further included resilient means for providing biasing between said resistance element assemblies and said shaft.

14. The potentiometer in accordance with claim 13 wherein said resilient means comprises a bowed washer positioned on said shaft.

15. The potentiometer in accordance with claim 1 wherein said fastener means comprise axially spaced apart retaining washers secured to said shaft. 

1. A ganged potentiometer comprising: a. a non-conductive wheel means having electrically conductive wiper means secured thereto and facing in axially opposite directions; b. a shaft extending through and supporting said wheel means for rotation about the axis thereof; c. a resistance element assembly mounted on said shaft proximate each end thereof, each said resistance element assembly including a non-conductive plastic base member, conductive plastic resistance track means and collector track means integral with said base member so as to be in contact with said wiper means during rotation of said wheel and terminal means adapted to electrically connect said resistance element assembly to a utilization device; d. key means integral with each said resistance element assembly and adapted to mate with a receptacle in a support member whereby rotation of said resistance element assemblies are pRevented relative to said wheel; and e. fastener means for minimizing relative axial movement of said resistance element assemblies and said wheel.
 2. The potentiometer in accordance with claim 1 wherein said wheel means is one piece and is loosely mounted on said shaft.
 3. The potentiometer in accordance with claim 1 wherein said wheel means is comprised of two separate and independent members, a wiper means being secured to each of said members.
 4. The potentiometer in accordance with claim 3 wherein said members are loosely mounted on said shaft.
 5. The potentiometer in accordance with claim 4 wherein there is further included spacer means intermediate said members.
 6. The potentiometer in accordance with claim 1 wherein said wheel means includes heat deformable boss means for securing said wiper means thereto.
 7. The potentiometer in accordance with claim 1 wherein said resistance element assemblies are loosely mounted on said shaft.
 8. The potentiometer in accordance with claim 1 wherein said resistance and collector track means are comolded with said base means.
 9. The potentiometer in accordance with claim 1 wherein said base members include heat deformable recesses for securing said terminal means thereto.
 10. The potentiometer in accordance with claim 1 wherein said key means comprises a non-circular boss extending from said base member in an axial direction away from said wheel.
 11. The potentiometer in accordance with claim 10, wherein said boss is rectangular.
 12. The potentiometer in accordance with claim 11 where the axis of said boss coincides with the axis of said shaft.
 13. The potentiometer in accordance with claim 1 wherein there is further included resilient means for providing biasing between said resistance element assemblies and said shaft.
 14. The potentiometer in accordance with claim 13 wherein said resilient means comprises a bowed washer positioned on said shaft.
 15. The potentiometer in accordance with claim 1 wherein said fastener means comprise axially spaced apart retaining washers secured to said shaft. 